PROJECT SUMMARY/ABSTRACT The prevalence of mental health problems among college populations has risen steadily in recent decades, with one-third of college students struggling with anxiety, depression, or an eating disorder. Yet, only 20-40% of college students with mental disorders receive treatment. Inadequacies in mental health care delivery result in prolonged illness, disease progression, poorer prognosis, and greater likelihood of relapse, highlighting the need for a new approach for detecting mental health problems and engaging college students in services. We have developed a transdiagnostic, low-cost mobile health targeted prevention and intervention platform that uses population-level screening for engaging college students in tailored services that address common mental health problems. This care delivery system represents an ideal model for service delivery given its use of our promising, evidence-based mobile programs, a transdiagnostic approach that addresses comorbid mental health issues, and personalized screening and intervention to increase service uptake, enhance engagement, and improve outcomes. Further, our service delivery model harnesses the expertise of our team of leaders in behavioral science, college student mental health, technology, and health economics, and bridges our team's work over the past 25 years in successfully implementing a population-based screening program in over 160 colleges and demonstrating the effectiveness of Internet-based programs for targeted prevention and intervention for anxiety, depression, and eating disorders in over 40 colleges. We propose to test the impact of this mobile mental health platform for service delivery in a large-scale trial across 20 colleges. Students who screen positive or at high-risk for clinical anxiety, depression, or eating disorders (excluding anorexia nervosa, for which more intensive medical monitoring is warranted), which account for a substantial proportion of the mental health burden on college campuses, and who are not currently engaged in mental health services (N=7,884; of 146,000 initially screened) will be randomly assigned to: 1) intervention via the mobile mental health platform; or 2) referral to usual care (i.e., campus health or counseling center). We will test whether the mobile mental health platform, compared to usual care, is associated with improved uptake (i.e., individuals beginning treatment) (Aim 1), reduced clinical cases and disorder-specific symptoms (Aims 2a, 2b), and improved quality of life and functioning (Aim 2c). We will also test putative targets/mechanisms, other mediators, predictors, and moderators of improved mental health outcomes (Aim 3) as well as stakeholder- relevant outcomes, including cost-effectiveness and academic performance (Aim 4). Our comprehensive mental health care platform can yield clinical benefit to students, appeal to university stakeholders, minimize barriers to implementation sustainability on campuses, and produce an economic return on investment compared to usual care. This population-level approach to service engagement has the potential to improve mental health outcomes for the 20+ million students enrolled in U.S. colleges and universities.